A simulation of Corot-2a with transiting hot Jupiter and starspots. (Simulation and photo by author).

We know more about our Sun than any other star because it gives us the opportunity to study solar activity up close. But just how normal is it? Recently, astronomers have been able to spy activity on other suns, teasing the data out of exoplanet transits. These are planets that happen to cross the tiny visible face of their parent star as seen from our line of sight and thus exhibit a tiny but measurable dip in their apparent brightness. Earlier this year, a team at the Hamburg Observatory has been refining this technique by monitoring the star Corot-2a. A younger Sun-like star, Corot-2a spins once every 4.5 earth days and possesses a transiting “hot Jupiter” which orbits once every 1.74 days. Examining a statistical analysis of the light curve as seen by the European Space Agencies’ (ESA) prolific Corot space observatory has yielded “notches” in the smooth curve, a tell-tale sign of “starspot” activity. This was conducted over 80 successive transits. The goal is to begin puzzling together a “butterfly diagram” for alien suns, much like the familiar 11 year cycle diagram yielded by Sporer’s Law for our own Sun. Doubtless, other suns follow different cycles, and this data will add to our understanding of stellar evolution. This will also answer such questions about our own Sun, such as; why do sunspots never form above a particular latitude? Are there larger interwoven cycles? And just what was our Sun like in its juvenile days?

Two tiny active regions (light spots) just starting to make themselves known…(credit: ESA/SOHO).

Something mildly bizarre is happening on our nearest star, the Sun. Or should we say, a lack there of… This weeks astro-event is a sort of non-event, but one of the big mysteries of 2009; where exactly are the sunspots? Turning that newly constructed white-light filter we built last week on our mild-mannered star shows a definite lack of activity in the solar photosphere. This isn’t entirely abnormal, as the Sun is just coming off of a solar minimum that occurs every 11 years. What is unusual is the length of this minimum; we’ve had over 600+ spotless days since 2004, a quarter of which have been in 2009 alone. A typical minimum consists of an average of 485 days. You have to go way back to 1913 to find such comparable a lull! Two tiny sunspots appeared last week, which prompted the discussion as to whether the latent solar cycle #24 is finally amping up or not. Both spots belong to the new cycle, their reversed polarity giving them away. Using the technique of helioseismology, Frank Hill and Rachel Howe at Tucson’s National Solar Observatory have discovered that the Sun’s internal dynamo isn’t dead, just sleeping. They predict that the subsurface tachocline should begin intersecting the surface at the junction of 22 degrees latitude by the end of 2009, and activity should resume. It’ll be a wait and see mystery that will only deepen if the spots don’t return to roost; and does this portend a stronger than usual maximum around the solar bend? Stay tuned!

This week’s astro-term of the week is Sporer’s Law. First worked out by astronomer Gustav Sporer, this law simply states that sunspots form at higher latitudes at the beginning of a solar cycle, and then gradually progress downward to lower latitudes in both hemispheres as the cycle progresses. We never see spots above 45 degrees of latitude, and astronomers aren’t quite sure why. The link between the solar cycle and the climate isn’t yet fully understood. Could a spotless Sun mimic or mask the effects of global warming? Both Earth and space bound telescopes are keeping a constant watch on our Sun. Cries of another Maunder minimum, a time from 1645 to 1715 that was marked by harsh winters and almost no sunspots were seen, may be a bit premature… cycle #24 were art thou?

Astro Documentaries

Pictured is a Delta IV rocket launch from Cape Canaveral on November 21st, 2010. The image is a 20 second exposure taken at dusk, shot from about 100 miles west of the launch site. The launch placed a classified payload in orbit for the United States Air Force.

DIY Astronomy

Difficult but not impossible to catch against the dawn or dusk sky, spotting an extreme crescent moon can be a challenge. The slender crescent pictured was shot 30 minutes before sunrise when the Moon was less than 20 hours away from New. A true feat of visual athletics to catch, a good pair of binoculars or a well aimed wide field telescopic view can help with the hunt.

The Sun is our nearest star, and goes through an 11-year cycle of activity. This image was taken via a properly filtered telescope, and shows the Sun as it appeared during its last maximum peak in 2003. This was during solar cycle #23, a period during which the Sun hurled several large flares Earthward. The next solar cycle is due to peak around 2013-14.

Astronomy Gear Reviews

Located in the belt of the constellation Orion, Messier 42, also known as the Orion Nebula is one of the finest deep sky objects in the northern hemisphere sky. Just visible as a faint smudge to the naked eye on a clear dark night, the Orion Nebula is a sure star party favorite, as it shows tendrils of gas contrasted with bright stars. M42 is a large stellar nursery, a star forming region about 1,000 light years distant.

Astronomical Observing Targets

Orbiting the planet in Low Earth Orbit (LEO) every 90 minutes, many people fail to realize that you can see the International Space Station (ISS) from most of the planet on a near-weekly basis. In fact, the ISS has been known to make up to four visible passes over the same location in one night. The image pictured is from the Fourth of July, 2011 and is a 20 second exposure of a bright ISS pass.

Next to the Sun, the two brightest objects in the sky are the Moon and the planet Venus. In fact, when Venus is favorably placed next to the Moon, it might just be possible to spot the two in the daytime. Another intriguing effect known as earthshine or ashen light is also seen in the image on the night side of the Moon; this is caused by sunlight reflected back off of the Earth towards our only satellite.

A mosaic of three images taken during the total lunar eclipse of December 21st, 2010. The eclipse occurred the same day as the winter solstice. The curve and size of the Earth’s shadow is apparent in the image.